Brain Damage

[antonis]

(Junk box BJT Fuzz/Dist/OD pedal)

Output various waveforms, from square to sawtooth, with almost numerous combinations of gain and clipping settings..



Q1/Q2 configuration is a high input impedance (about 3M) CFP with 3X gain..

Q3 stage is a variable gain CE amp of 5.6X gain (15dB) up to 1,300X (62dB)..

Q4 is an Emitter follower serving both for Q3 Collector partial resistance bootstrapping (via Gain SW and C4) and for Q5/Q6 hard clipping configuration drive..

(Q5/Q6 preferred for their more abrupt clipping, due to less current needed, compared with ordinary Si diodes..)

CAP SW (SPDT ON-OFF-ON) selects between 100nF (OFF), 320nF (ON 1) and 570nF (ON 2), considerably altering clipped waveform, in conjunction with Rx value (1k proposed)..

Clipping configuration is bypassed via CLIP SW (DPDT)..

Q7 is a humble Emitter follower serving both for relatively high input impedance seen by clipping configuration and TONE control input isolation..

TONE configuration an active (via Q8/Q9) TILT control, shamelessly stolen from Electricdruid's Hard Bargain circuit..


Finally, Q8 is a CE amp of 120X gain (41dB) and Q9 is an output buffer..

[antonis]

A bit tight layout..

[deadastronaut]

i saw the title and thought of me...

cool. 

[Ben N]

A bit tight layout..

A BIT??

[garcho]

Bravo, we need more Antonis designs around here.

[duck_arse]

i saw the title and thought of me...

cool. 

yeah, so did we.

[antonis]

i saw the title and thought of me...

I saw you and thought the title..

[GibsonGM]

I couldn't read the title due to paint fumes...

[diffeq]

Finally, Q8 is a CE amp of 120X gain (41dB) and Q9 is an output buffer..

I thought of the title when I saw R20 and R21 being 4k7 and 3k9... then I saw C14.

[antonis]

Finally, Q8 is a CE amp of 120X gain (41dB) and Q9 is an output buffer..

I thought of the title when I saw R20 and R21 being 4k7 and 3k9... then I saw C14.